This invention relates to a preform and container and a method to make said preform and container by providing at least two polymeric layers with different blowing temperatures, wherein at least one additive is present. The additive(s) exist in quantities sufficient to cause the polymeric layers to heat to their respective blow temperatures in the same or essentially the same period of time.
Energy absorbing materials such as carbon black and graphite have been used in polymeric materials to reduce heat up time. Pengilly, U.S. Pat. No. 4,408,004 discloses the use of carbon black in PET in a range from less than 10 parts per million (ppm). The carbon black can be added at any stage of the polyester preparation, such as the esterification or the transesterification reaction or at the condensation stage. The Example of the ""004 patent show that the carbon black can be added in controlled quantities such that the polymer heats up faster but still produces a high clarity, low haze polymer.
Laser imageable assemblies comprising transparent material have called for the use of carbon black and/or graphite as energy absorbing material. In U.S. Pat. No. 4,711,834, a disclosure is made to use graphite and carbon black in a binder resin in amounts such that the weight ratio of particles to binder resin is 10:1 to 1:2. The polymeric material discussed includes the terephthalic acid and the 2,6 (NDC is 2,6, but some work does contemplate 2,7) -naphthalene dicarboxylic acid, each combined with ethylene glycol. These energy-absorbing materials are dispersed in the heterogeneous resin layer to absorb energy passing through the layer.
Containers, most specifically bottles, have been developed to hold food and beverages comprised of polymeric materials such as PET and PEN. The art also indicates that both PEN and PET layered bottles can be used to attain the benefits of some of the barrier properties of the PEN with the cost efficiency of the PET. Other disclosures have lined these polymers with substrates such as aluminum or glass to also achieve high barrier, low cost properties.
While these concepts have been disclosed for PEN and PET, no successful bottle has been made from the strain hardenable versions because of the significant difference in blowing temperature of PEN and PET. When one heats that multi-layer structure at the same rate, the PEN is either too cold to blow or the PET is too hot to blow. This problem was described in 1994. (Excerpt from BevPak Americas 1994, Sisson, Callander, xe2x80x9cHigh Performance PEN and Naphthalate Based Packaging Resinsxe2x80x9d, Presented Apr. 11, 1994.)
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This is important, particularly for those interested in co-injection or multilayer structures. Previous work with PEN homopolymer/PET structures indicates that the melt points and the Tgs of the PEN and PET homopolymers were too far apart for a two step process. In the injection step, the heat required to melt the PEN would crystallize the PET and in the reheat step, the temperature required to reach PENs Tg was too great for the PET.xe2x80x9d
Some art discloses PEN as an example of an inner layer. However, the PEN described is a highly modified copolymer such that is not strain hardenable. It has no melting point or crystalline type conditions. This limits this art to the properties of an essentially amorphous PEN with substantially less naphthalate. In addition to not maximizing the properties for the amount of PEN, the amorphous materials are costly to dry and process relative to a crystalline material.
The problem addressed in this invention is the fact that multilayers of PEN/PET polymers cannot be reheat blown with traditional formulations. Recognition is made of the difference in the Tg values between PEN and PET. This large difference creates two separate blow windows which do not overlap and has thus made it difficult to make a multilayer PET/PEN bottle using a reheat blow process from a preform.
This invention provides substantial improvements over the art. By changing the heating rate of the PEN (or PET or both) so that it or they reaches its higher blow temperature at the same time the PET reaches its lower blow temperature, one can now incorporate crystallizable and strain hardenable PEN""s and their advantages of orientation and processing.
This invention describes a multilayer polymeric preform or container wherein the blow temperatures of each polymer layer is controlled by the addition of a faster heat up rate additives such that the polymer layers in the preforms blow at the same relative period of time to make the container.